A comprehensive guide to best practices, native defences, and advanced vendor solutions for securing your Microsoft 365 environment — from foundational controls to cutting-edge AI-driven protection.
The Foundation: Microsoft 365 Native Security
Before layering on advanced tools, every organisation must understand and master the built-in security capabilities that Microsoft 365 provides. This chapter explores the core pillars, shared responsibilities, and essential practices that form the bedrock of a resilient security posture.
Understanding the Shared Responsibility Model
Microsoft's Responsibility
Microsoft secures the underlying cloud infrastructure — the physical datacentres, networking, virtualisation layers, and the platform itself. These components are managed, patched, and protected on your behalf.
Your Responsibility
Everything within the cloud remains yours to protect. This includes your configurations, end-user devices, identities and access controls, and the data you store and share.
Core Microsoft 365 Security Pillars
Security & Risk Management
Proactive risk assessment powered by machine learning-driven threat detection. Continuously evaluates your environment to surface emerging vulnerabilities before they are exploited.
Information Protection
Data Loss Prevention (DLP) policies and Information Rights Management (IRM) ensure sensitive data is classified, labelled, and protected against accidental or malicious exposure.
Threat Protection
Microsoft Defender for Office 365 delivers anti-malware, advanced anti-phishing, Safe Links, and Safe Attachments — providing layered defence across email and collaboration tools.
Essential Best Practices for SMBs
Organisations with up to 300 users can dramatically reduce risk by implementing these foundational controls. These are high-impact, low-complexity steps that should be non-negotiable across every Microsoft 365 deployment.
Multi-Factor Authentication
Enabled by default via Security Defaults. For more granular control, Conditional Access policies allow MFA enforcement based on user risk, location, and device compliance.
Admin Account Protection
Privileged accounts require dedicated security measures: separate admin accounts, Privileged Identity Management (PIM), and strict access reviews to limit exposure.
Preset Security Policies
Microsoft's Standard and Strict preset policies apply proven, Microsoft-recommended threat settings tailored to your organisation's risk profile with minimal configuration effort.
Device Protection
Every device accessing company data must be enrolled and compliant. Microsoft Intune enables mobile device management (MDM) and mobile application management (MAM) at scale.
Elevating Your Defence: Advanced Vendor Solutions
Native Microsoft 365 security tools provide a solid starting point, but the threat landscape demands more. This chapter examines how specialised third-party solutions address the gaps that built-in controls leave open — and why leading organisations are investing in them.
Beyond Native: Addressing Evolving Threats
The Limitations of Native Tools
Microsoft 365's built-in security features are powerful, but managing them at scale can be complex. Security teams often face overwhelming alert volumes, leading to alert fatigue — where critical signals are missed amidst the noise. Advanced attacks such as Business Email Compromise (BEC) and account takeovers are specifically engineered to evade standard defences.
The Human Factor
74%
of all breaches exploit human vulnerability — through phishing, credential theft, or social engineering. Technology alone cannot close this gap without behavioural intelligence layered on top.
Abnormal AI: Behavioural Analysis for Microsoft 365
Abnormal AI redefines email security by building a behavioural baseline for every user and entity in your organisation — detecting anomalies that rule-based systems simply cannot catch.
Precise Protection
Complements native Microsoft defences against sophisticated email threats and account takeover attacks, catching what Defender misses.
API-Native Integration
Deploys in minutes via Microsoft Graph API — no MX record changes required, ensuring zero disruption to existing mail flow.
Automated SOC Operations
Streamlines alert triage, remediation workflows, and reporting — reducing manual SOC workload by automating repetitive response tasks.
Microsoft Teams Security
Extends protection beyond email — monitoring Teams chats and channels for suspicious links, malicious files, and unusual behaviour patterns.
Abnormal AI: Enhancing Security Posture
Closing Configuration Gaps
Abnormal continuously scans your Microsoft 365 environment for security misconfigurations — automatically identifying and remediating issues without requiring manual intervention from your IT team. This removes a significant source of ongoing risk that often goes undetected in complex tenants.
Benchmarking Against Best Practices
Security posture is measured against CIS (Centre for Internet Security) benchmarks, with risks prioritised based on real-world threat intelligence rather than theoretical severity scores alone.
CoreView: Purpose-Built Security Posture Management
CoreView is designed specifically for Microsoft 365, providing deep visibility and automated governance across every workload in your tenant — from Entra ID to Intune to Defender.
Continuous Monitoring
Detects risks in real time across all M365 workloads including Entra, Intune, and Defender — providing a single pane of glass for security oversight.
Automated Remediation
Resolves security issues instantly, with coverage spanning over 8,000 configuration details — eliminating the need for manual remediation at scale.
Risky Guest Access & Sharing
Detects and remediates vulnerabilities arising from overpermissioned guest accounts and insecure external sharing configurations across SharePoint and Teams.
Identity Best Practices
Enforces MFA and password policies across the tenant, ensuring compliance with identity security standards and reducing the risk of compromised credentials.
Proactive Security: The Path Forward
Reactive security is no longer sufficient. This chapter outlines how organisations can build a proactive security programme — progressing from foundational controls to advanced, AI-powered defences — and why the cost of inaction far outweighs the investment in getting it right.
The "Crawl, Walk, Run" Framework
Effective security maturity doesn't happen overnight. Organisations that try to implement everything at once often end up with gaps everywhere. A phased approach ensures each layer is solid before the next is added.
Crawl: Build the Foundation
Enable MFA, apply Security Defaults, configure preset security policies, and enrol devices. These basics prevent the majority of common attacks and cost-effective to implement.
Walk: Layer Advanced Protections
Introduce Conditional Access, Privileged Identity Management, and third-party solutions like Abnormal AI to address gaps that native tools cannot cover.
Run: Optimise and Automate
Deploy posture management tools like CoreView, automate remediation workflows, and continuously benchmark against industry standards as your security expertise matures.
The Cost of Misconfiguration
Misconfiguration is the silent killer of cloud security. Unlike dramatic breaches, misconfigurations often go undetected for months — and by the time they're discovered, the financial and reputational damage is severe.
Days to Identify
Average time to identify a breach caused by cloud misconfiguration — nearly half a year of undetected exposure.
Average Breach Cost
The average total cost of a data breach tied directly to a cloud or SaaS misconfiguration, including investigation, remediation, and regulatory penalties.
Affected Organisations
Of organisations have reported at least one security incident directly attributable to SaaS misconfiguration in the past 12 months.
Strategic Vendor Integration
Closing the Gaps Cost-Effectively
Supplementing Microsoft 365's native security with targeted third-party solutions is not only strategically sound — it is often more cost-effective than the alternative of a breach. Solutions like Abnormal AI and CoreView are purpose-built to integrate seamlessly with Microsoft 365, addressing specific attack vectors and configuration risks that built-in tools are not optimised to handle.
AI as a Force Multiplier
Leveraging AI-driven platforms enables security teams of any size to punch above their weight — automating detection, triage, and remediation tasks that would otherwise demand significant headcount and expertise.
Key Integration Benefits
- Rapid deployment with minimal disruption to existing workflows
- Reduced alert fatigue through intelligent prioritisation
- Automated posture management across 8,000+ configuration points
- Real-time detection of BEC, account takeover, and insider threats
- Measurable ROI through breach cost avoidance
Your Next Step: A Proactive Security Stance
The journey to a resilient Microsoft 365 security posture is continuous — but every organisation can start today with clear, high-impact actions.
Know Your Responsibilities
Understand exactly where Microsoft's responsibility ends and yours begins. Close every gap in your configurations, identities, and data governance.
Implement MFA and Admin Security
Enable Multi-Factor Authentication across all users and apply dedicated protection to privileged accounts — the single most impactful action you can take today.
Monitor Continuously
Adopt continuous posture management to detect and remediate misconfigurations in real time, rather than relying on infrequent point-in-time audits.
Invest in Advanced Solutions
Stay ahead of evolving threats by integrating AI-driven tools like Abnormal AI and CoreView to address the gaps that native Microsoft 365 security cannot cover alone.
Security 365: Mastering Microsoft 365 CyberCloud Security